. A new thermo-electric fluid-meter and hot-wire anemometer. vanometer aoale for eaoh oouple. 138 o o to CO o M o ft 8 3 03O ^ i EH 03 M03 03 •»• pa • oo iO o O00 • • O CO • oo • : \ 00 o to o • to • oo • to 111 1 t1111 1tI 11 • oo tO «0 oo •M o H • 00 Cvl lOM *CD 1111 1 COH • to to • M •HH •oo « H 0000 • H •H •H B- • H oa* •o 00 M • M to B• • oo CO to CM to • kO to • to • CD toca •eo eo •e» to H • to H lOH • • o ooo iH H • •11• •111 ••11 o •to EO • 00 • a 9 § 9 •H ?P« 60 « <Di-l M a o o e C B B B B Positive Element HO o •H + 00 I eo 1 1 «* to •H?^ to! a* .ao toto -•- • PiO o 139 o c) M • O
. A new thermo-electric fluid-meter and hot-wire anemometer. vanometer aoale for eaoh oouple. 138 o o to CO o M o ft 8 3 03O ^ i EH 03 M03 03 •»• pa • oo iO o O00 • • O CO • oo • : \ 00 o to o • to • oo • to 111 1 t1111 1tI 11 • oo tO «0 oo •M o H • 00 Cvl lOM *CD 1111 1 COH • to to • M •HH •oo « H 0000 • H •H •H B- • H oa* •o 00 M • M to B• • oo CO to CM to • kO to • to • CD toca •eo eo •e» to H • to H lOH • • o ooo iH H • •11• •111 ••11 o •to EO • 00 • a 9 § 9 •H ?P« 60 « <Di-l M a o o e C B B B B Positive Element HO o •H + 00 I eo 1 1 «* to •H?^ to! a* .ao toto -•- • PiO o 139 o c) M • O •«< P«tH in • 4* « « O 9 •H O «w d o +»« mo P« 9» m * « * *» *? * o M o o I to O I •ri *00 » o o CO to 9 PiO o uo s I II I I I. 141 THE LeCHATELIER PYROMETER. In measuring temperatures between 200^and 1600° C, thermocouples oonsisting of a wireof rhodium alloy of platinum, joined to a wire ofpure platintuo, have been found to be most appro-priate. The most common and widely used of thistype consists of a wire of 10^ rhodium alloy withplatinum. Joined to one of pure platinum, and isknown as the LeChatelier pyrometer. For a thermo-junction of this type the relation existing betweenth« electromotive force. fE) and the temperature ofthe hot Junction (t), in the interval of temperaturesfrom SOO* to 1200° C, is quite accurately given bythe equation,(1) B a a + bt 4-ct2 when the cold Junctions are at 0° C* When thisequation is extrapolated to higher temperaturesthan 1200° C«, it gives lower than the correctvalue of temperatures. As an example, the meltingpoint of platinum is found to be 1710° C» by thisequation, instead of 1750° C. or higher, as given byrecent work. 142 The Holman •qustion expreBsea the re
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